In the field of electricity generation, there is often a mismatch between supply of electricity and the demand for the electricity at any given time.
As an example, it is often more efficient to continuously run power stations as opposed to intermittently running them to match demand. However, given that demand for electrical energy continuously fluctuates (particularly at night when demand drops significantly) supply of electrical power from the power station may frequently exceed the level of demand. As a further example, renewable power generators often produce fluctuating levels of energy due to the unpredictable and changeable nature of renewable sources (e.g. wind power, wave power, solar intensity etc.) and this time dependent output seldom matches the demand. Thus, there is a need for energy storage systems that may be used to store energy produced by electricity generators (e.g. when demand for such energy is low), and subsequently be capable of converting stored energy back into electrical energy (e.g. when demand increases).
Several energy storage systems are known and these include systems that convert electrical energy into thermal energy which is subsequently stored for later use.
Pumped-storage hydroelectricity (PSH) is currently the most effective energy storage solution available on a large scale. However, PSH requires a mountain and lake/reservoir in order to benefit from its high round trip efficiency. Other large scale energy storage solutions have been mooted, though they often require other geographically constrained features (e.g. salt caverns), complicated cryogenic plants and batteries (which not only have a limited effective life making their economics questionable, but also require climate controlled environments which adds a parasitic loss and presents significant safety issues) or have high costs associated with decommissioning and disposal of hazardous materials at end of life.
Many industrial and commercial processes produce waste energy in the form of heat. The ability to capture this waste heat and convert it in to usable power has both financial and environmental benefits. There is therefore a need to both store energy and/or capture waste heat.
It is an object of certain embodiments of the present invention to overcome certain disadvantages associated with the prior art.
It is an object of certain embodiments of the present invention to store energy and/or capture waste heat and convert the waste heat into useful energy.